Under cold start conditions, an engine has cooled to ambient conditions, which may be relatively hot or cold, and each component of the engine warms-up to a desired operating temperature. During this time, there may be high friction within the engine due to a higher viscosity of engine fluids such as engine oil when they are relatively cold, and further, heat may be lost to engine coolant thereby reducing a thermal efficiency of the engine. Overall, these effects may lead to a lower fuel economy, for example.
The inventors herein have recognized the above problems and have devised an approach to at least partially address them. Thus, a method for heating a turbocharged engine in a vehicle is disclosed. The method comprises, during a cold engine start and after light-off of an exhaust catalyst, initiating operation of a high-pressure exhaust gas recirculation system (HP-EGR) by opening a HP-EGR valve, the HP-EGR system having a cooler which is part of an engine coolant circuit, and adjusting an engine operating parameter based on combustion stability in order to increase an amount of HP-EGR.
By using HP-EGR to heat the coolant, fuel economy may be improved without adding additional components to the engine system for coolant heating. Further, engine coolant temperature may be increased at a high rate due to the relatively low temperature of the engine coolant compared to the exhaust gas temperature leading to improved fuel economy during the cold start. Moreover, increasing an amount of HP-EGR before the engine is warmed-up may reduce combustion stability; therefore, by adjusting one or more engine operating parameters such as cam timing and fuel injection, combustion stability may be maintained.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.